We were discussing the concept of laminar
and turbulent flow, Reynolds
experiment, frictional
loss in pipes, derivation of expression
for loss of head due to friction in pipes, co-efficient
of friction in terms of shear stress, basics
of shear stress in turbulent flow and also the minor head losses in pipe flow, in the subject of fluid mechanics, in our recent posts.

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Where,
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Now we will go ahead to see the concept of hydraulic
gradient and total energy line, in the subject of fluid mechanics, with the help
of this post.

Concepts of hydraulic gradient line and total energy
line will be quite useful when we analyze the problems of fluid flow through
pipes. Now we will understand here the concept of hydraulic gradient line and
total energy line.

Hydraulic gradient line and total energy line are
the graphical representation for the longitudinal variation in piezometric head
and total head.

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**Hydraulic
gradient line **

Hydraulic gradient line is basically defined as the
line which will give the sum of pressure head and datum head or potential head
of a fluid flowing through a pipe with respect to some reference line.

Hydraulic gradient line = Pressure head + Potential
head or datum head

H.G.L = P/ρg + Z

Where,

H.G.L = Hydraulic gradient line

P/ρg = Pressure head

Z = Potential head or datum head

###
**Total
Energy Line **

Total energy line is basically defined as the line
which will give the sum of pressure head, potential head and kinetic head of a
fluid flowing through a pipe with respect to some reference line.

Total energy line = Pressure head + Potential head +
Kinetic head

H.G.L = P/ρg + Z + V

^{2}/2g
Where,

T.E.L = Total energy line

P/ρg = Pressure head

Z = Potential head or datum head

V

^{2}/2g = Kinetic head or velocity head

###
**Relation
between hydraulic gradient line and total energy line **

H.G.L = E.G.L - V

^{2}/2g
Let us see the following figure, there is one
reservoir filled with water and also connected with one pipe of uniform
cross-sectional diameter.

Hydraulic gradient and energy lines are displayed in
figure.

At Velocity V = 0, Kinetic head will be zero and
therefore hydraulic gradient line and energy gradient line will be same.

At Velocity V = 0, EGL = HGL

Further we will go ahead to find out the basic concept of flow through syphon in the subject of fluid mechanics, with the
help of our next post.

You can find out some very important posts based on this category such as pumps and basic pumping system, total head developed by the centrifugal pump, parts of centrifugal pump and their function, heads and efficiencies of a centrifugal pump.

You can find out some very important posts based on this category such as pumps and basic pumping system, total head developed by the centrifugal pump, parts of centrifugal pump and their function, heads and efficiencies of a centrifugal pump.

Do you have any suggestions? Please write in comment
box.

### Reference:

Fluid mechanics, By R. K. Bansal

Image courtesy: Google

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